Process of making ferrochromium



Patented Oct. lfl, 1924.

UNITED STATES PATENT OFFICE.

'KARL WEEK, OF E SS EN, GERMANY, ASSIGNOR TO METAL THERMIT CORPORA- TION, OF NEW YORK, N. Y., .l CORIORATION OF NEW JERSEY.

PROCESS OF MAKING FERROCHROMIUM.

No Drawing.

To all whom it may concern:

Be it known that I, KARL Mt'ILLeR, a cit-izen of the German Republic, and residing at Essen, Germany, have invented a new and useful Improvement irf'Processes of Making Ferrochromium (for which I filed application in Germany October 14, 1919); and I do hereby declare the following to a full, clear, and exact description of the same.

Some years ago it was found that, in the aluminothermic production of carbon-free ferro -chromium from chrome-iron ore, the previously inferior yield of chromium (about 70%) can be increased (by about 15 to 20 per cent) by adding chromic oxide to the mixture of chrome-iron ore and aluminum (or any other reducing metal or alloy actingvin the same manner). In this way it is possible to produce ferro-chromium of constant or uniform composition with a satisfactoryyield of chromium from chromeiron ore. However, this process cannot now be economically used in practice owing to the fact that the cost of chromium oxide has very greatly increased,in comparison with the price paid some years ago.

I have made the unexpected discovery that the same increased yield of chromium from chrome-iron ore can be obtained by the aluminothermic process, and also that carbon-free ferro-chromium of constant and uniform composition can be produced by adding oxides of iron to the usual aluminothermic mixture of chrome-iron ore and reducingmetal or metals and then subjecting this mass .to the aluminothermic reaction.

In this wva it is also possible to increase the yield of c romium from the chrome-iron ore. by, say, 15 to 20 per cent, and to produce ferro-chromium of any desired composition.

For carrying out the process in practice, I preferably make use of rolling-mill scale which forms a 'well known b -product, in the rolling of iron and steel: and which therefore, can be obtained in an desired quantities at a very low price. his rolling-mill scale consists of a mixture or comp)ound of iron oxides, mainly FeO and Fe,

By way of example, the following alumi- Serial No. 496,633.

no-thermic mixture may be employed for the purpose of producing carbon-free ferro-chromium, to-wit, approximately 70% of chrome iron ore, 22% of aluminum and 8% of mill scale. It will be understood that this is merely a specific instance and, obviously, the invention contemplates the employment of such relative pro-portions of the ore and aluminum as are ordinarily regarded as necessary and proper for carrying out the alumino-thermic production of ferro-chromium, to which mixture isaddedsufiicient oxide of iron, in any appropriate form, to efi'ect the desired increase in the chromium content of the resultant alloy.

Bypreheating the mixture of chromeiron ore, iron oxides and aluminum before subjecting same to the aluminothermic reaction, it is possible to obtain a particularly advantageous and uniform yield of chromium (in the shape of carbon-free ferro-chroinium) from chrome-iron ore.

It may be mentioned, also, that multiple alloys of ferro-ch-romium can be produced by adding other oxides of metals such, for instance, as oxides of cobalt, nickel, tungsten, molybdenum or vanadium.

What I claim is:

1. The process for-increasing the yield of chromium in the aluminothermic production of carbon-free. iron-chromium alloys from chrome-iron ore, which consists in adding to the ordinary aluminothermic mix.- tureof chrome-iron ore and reducing metal a certain amount of oxides of iron and subjecting this mass to the aluminothermic reaction.

2. The process for increasing the yield of chromium in the aluminothermic production of carbon-free iron-chromium alloys from chrome-iron ore, whichconsists in adding,

to the ordinary aluminothermic'mixture of chrome-iron ore and reducing metal a certain amount of rolling-mill scale and subjecting this mass to the aluminothermic reaction.

3. The process for increasing the yield of chromium in the aluminothermic production of carbon-free iron-chromium alloys from chrome-iron ore, which consists in adding to the ordinary aluminothermic mixture of chrome-iron ore and reducing metal" a certain amount of oxides of iron and oxides of other metals for the purpose of producing multiple alloys of term-chromium.

4. The process for increasing the yield of chromiumin the aluminothermic produc- 5 tion of carbon-free iron-chromium alloys from chrome-iron ore, which consists in adding to the ordinary aluminothermic mixture of chrome-iron ore and reducing metal a certain amount of rolling-mill scale and 10 oxides of other metals for the purpose of producing multiple alloys of ferro-chromium.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

DR. KARL MULLER.

Witnesses:

AUGUST WALKER, FRITZ RUHL'. 

